The present invention relates to improvements in machines for making steno pads, exercise books and analogous stationery products, and more particularly to improvements in machines for making stationery products (hereinafter called pads for short) wherein the sheets or leaves are held together by a film of adhesive which is applied to one edge face of each pad.
It is already know to convert stacks of overlapping paper sheets into pads by introducing the stacks into the pockets of a circulating conveyor wherein the pockets are equidistant from one another and which is indexed through increments of predetermined magnitude. The conveyor is further equipped with means for releasably holding the stacks in the respective pockets and cooperates with an orienting device which aligns the sheets of successive stacks prior to the application of adhesive, as well as with an adhesive applying device which applies a coat or film of adhesive to each stack which has advanced beyond the aligning device. Suitable feeding means is provided to admit stacks of paper sheets into the pockets of the conveyor at a first station, and a suitable removing means is provided to accept finished pads from the pockets of the conveyor at a second station. Reference may be had to German Pat. No. 22 25 527 which discloses a machine for the making of books consisting of printed forms or the like. However, the same principle can be resorted to in connection with the making of ruled pads or analogous stationery products.
An advantage of the machine which is disclosed in the German patent is that the path of pockets in the circulating conveyor, the stack feeding means and the pad evacuating means are disposed in a common vertical plane. This means that the stacks and the pads are invariably transported in a single direction (meaning in the aforementioned vertical plane) instead of moving from a first vertical plane into another verticsl plane as is customary in certain older types of pad making machines. The placing of the stack feeding means, of the pad removing means and of the circulating conveyor (which transports the stacks during conversion into pads and thereupon transports the pads to the removing means) is desirable and advantageous because such machines take up little room which is particularly important when such a machine is installed in a complete production line wherein webs of paper coming from one or more reels are subdivided into sheets, wherein the sheets are stacked, wherein the stacked sheets are converted into pads, and wherein the pads are stacked prior to insertion into cardboard boxes or the like. For example, it is known to install a pad making machine in a production line wherein a web unwinding unit is followed by an imprinting unit which is followed by a cross cutting unit preceding a sheet overlapping unit which, in turn, precedes a sheet counting and stacking unit. The latter is followed by a cover applying unit which precedes the binder applying unit located ahead of a trimming and severing unit. In such production lines, the placing of the aforeenumerated units one after the other along a straight line is of advantage for a number of reasons, such as the possibility of greatly increasing the output of the production line as a result of a pronounced increase of cycles per unit of time. This is possible because the sheets or stacks of sheets invariably advance in parallelism with their shorter edges, irrespective of whether they are transported along straight or arcuate paths. Such mode of transporting the sheets, stacks and pads allows for operation with relatively short advancing strokes or steps.
Production lines of the above outlined character are used for the making of pads wherein the sheets are held together by spiral binders or the like. The sheet feeding means is disposed substantially diametrically opposite the pad removing means with reference to the axis of the conveyor whose pockets transport stacks away from the feeding means and deliver pads to the removing means. If such teaching is transferred into the field of making pads whose sheets are held together by an adhesive, the conveyor which transports stacks from the feeding means and delivers pads to the removing means is used only to 50 percent of its capacity. On the other hand, a freshly formed pad (i.e., a stack one edge face of which was coated with a film of adhesive) must remain on the conveyor for a certain period of time in order to allow for setting of the adhesive prior to removal of the pad from its pocket. This means that the conveyor must be formed with a very large number of pockets or that the conveyor must be indexed at a relatively low frequency. Consequently, such a conveyor is either too bulky or it constitutes a bottleneck in the production line and necessitates a slowdown of other units with attendant losses in output. In other words, if the conveyor has a relatively small number of pockets, it prevents the operation of other units in the production line at their maximum capacity.
Attempts to overcome the drawbacks of the aforediscussed production line in connection with the making of pads whose sheets are held together by an adhesive include a departure from the straight-line operation, i.e., the stack feeding means and the pad removing means are placed close to one another so that each stack can remain on the conveyor while the latter completes a little less than one full revolution. The pads are removed in a direction substantially at right angles to the direction of advancement of stacks toward the circulating conveyor. As a rule, the stack feeding means is installed at a level directly above the pad removing means so that, if the stacks are fed by moving them along a horizontal path, the removed pads are advanced downwardly along a vertical path. It is also known to feed stacks into the pockets and to remove pads from the pockets at right angles to the plane of orbital movement of the pockets. All such departures from the preferred straight-line concept are resorted to in an effort to prolong the period of dwell of pads in their pockets and to thus allow the adhesive films on the edge faces of the pads to set prior to manipulation of the pads, i.e., prior to removal of pads from their pockets and prior to transport of removed pads to a stacking, trimming, severing or other unit. It has been found that, though the just discussed attempts in fact prolong the periods during which the adhesive films are allowed to set, they invariably contribute to complexity of the machines and reduce the output of such machines below the output of comparable machines whose operation is based on the straightline principle and which utilize spiral binders or the like in lieu of adhesive paste. Moreover, the space requirements of such machines are quite substantial which is especially undesirable when the machines are installed in complete production lines whose space requirements are often enormous so that compactness of individual units is evidently an important advantage.